linux-kernel - [PATCHv2 1/2] init: Move stack canary initialization after setup

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Message-Id: <20170816224650.1089-2-labbott@redhat.com>
Date:   Wed, 16 Aug 2017 15:46:49 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Laura Abbott <lauraa@...eaurora.org>,
        kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Micay <danielmicay@...il.com>,
        Laura Abbott <labbott@...hat.com>
Subject: [PATCHv2 1/2] init: Move stack canary initialization after setup_arch

From: Laura Abbott <lauraa@...eaurora.org>

Stack canary intialization involves getting a random number.
Getting this random number may involve accessing caches or other
architectural specific features which are not available until
after the architecture is setup. Move the stack canary initialization
later to accomodate this.

Signed-off-by: Laura Abbott <lauraa@...eaurora.org>
Signed-off-by: Laura Abbott <labbott@...hat.com>
---
v2: Also moved add_latent_entropy per suggestion of Kees.
---
 init/main.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/init/main.c b/init/main.c
index 052481fbe363..21d599eaad06 100644
--- a/init/main.c
+++ b/init/main.c
@@ -515,12 +515,6 @@ asmlinkage __visible void __init start_kernel(void)
 	smp_setup_processor_id();
 	debug_objects_early_init();
 
-	/*
-	 * Set up the initial canary ASAP:
-	 */
-	add_latent_entropy();
-	boot_init_stack_canary();
-
 	cgroup_init_early();
 
 	local_irq_disable();
@@ -534,6 +528,11 @@ asmlinkage __visible void __init start_kernel(void)
 	page_address_init();
 	pr_notice("%s", linux_banner);
 	setup_arch(&command_line);
+	/*
+	 * Set up the the initial canary and entropy after arch
+	 */
+	add_latent_entropy();
+	boot_init_stack_canary();
 	mm_init_cpumask(&init_mm);
 	setup_command_line(command_line);
 	setup_nr_cpu_ids();
-- 
2.13.0